The following experiments are planned: (a) effects of continuous light in the rat on the sequences of hormonal and ovarian events in the first cycle after onset of continuous light; (b) effects of grouping of female mice on prolactin secretion during a 24 hour period; (c) performance of ovariectomy and/or adrenalectomy on metestrus on serum steroids and gonadotrophins during the next 24 hour period; (d) performance of ovariectomy, with and without adrenalectomy, on serum LH and FSH at 24 hour intervals for six days to detect time of LH rise; (e) injection of LH intravenously into pentobarbital-blocked proestrous rats and sample estrogen, progesterone, LH and FSH at frequent intervals (by terminal samples) during the next 24 hours; (f) inject pentobarbital on the day before proestrus and sample gonadal steroids and gonadotrophins in the serum during the next 48 hours.